The present technology relates to an optical unit, an imaging device, an electronic apparatus, and a master, and more particularly, to an optical unit having an antireflection function.
An example of antireflection techniques of the related art is a technique for suppressing surface reflection by forming a multilayered coating film or a nanostructure on a surface. Among such techniques, a technique for forming a nanostructure on a surface is particularly attracting people's attention since an antireflection effect can be exhibited for a relatively wide wavelength range.
Japanese Patent No. 4404161 discloses a technique for suppressing surface reflection by forming a wave surface on the surface of a base member by two-dimensionally arranging a plurality of nanostructures on the surface of the base member. As the nanostructures, nanostructures having a projecting shape with respect to the surface of the base member (for example, see FIG. 2) and nanostructures having a recessed shape (pits) with respect to the surface of the base member (for example, see FIG. 18) are disclosed.
Hitherto, concerning nanostructures having a projecting shape with respect to the surface of a base member, a study has been extensively conducted on the shapes of projections that may improve antireflection characteristics. However, it is also desirable to improve antireflection characteristics for nanostructures having a recessed shape (pits) with respect to the surface of a base member. Particularly, among wave surfaces constituted by such nanostructures having a recessed shape, it is desirable to improve antireflection characteristics for a wave surface having a curved plane which curves in a recessed shape between an apex and a bottom of the wave surface.